London fire could delay deal between UK PM May's Conservatives and DUP

Referring to speculation that negotiations could be extended until March 2019, Barnier said: "If we work seriously, I see neither the usefulness nor the interest of pushing back this date".

Barnier and British Brexit Secretary David Davis will open the talks on Monday at 11 a.m.in Brussels and they'll continue on Tuesday with top officials from the European Commission and the U.K.'s Brexit department.

May has a busy schedule today, hosting a cabinet meeting and talks with the DUP leader before travelling to Paris to meet French President Emmanuel Macron.

European Union officials acknowledge that the agreements to be reached before Britain leaves in March 2019 can only be concluded as a whole package simultaneously but leaders have barred Barnier from talking about trade before he gets outline deals on the rights of expatriate citizens and how much Britain owes the EU.

Nearly a year after Britain voted to leave its biggest market, the talks come amid signs the U.K.is softening its approach to the split and adopting a more conciliatory tone.

Speaking as he arrived for a meeting of European Union finance ministers in Luxembourg, he said: "As we go into that negotiation, my clear view - and I believe the view of the majority of people in Britain - is that we should prioritise protecting jobs, protecting economic growth and protecting prosperity as we enter those negotiations and take them forward".

"Discussions are going well with the government and we hope soon to be able to bring this work to a successful conclusion", Foster tweeted.

Guy Verhofstadt, the European Parliament's chief Brexit negotiator, warned the United Kingdom risks a "brutal exit" if discussions aren't concluded within two years. "It will be a brand new door, with a new Europe, a Europe without rebates, without complexity, with real powers and with unity", Verhofstadt said.

May has not yet responded to a proposal from some Conservatives for business groups and MPs from all parties to agree a national position on Brexit.

Meanwhile, the chief European Union negotiator has told the Financial Times that the clock was ticking on Brexit talks, and that Britain should be wary of further delays.

Sir John Major is one of those urging caution.

The performance of the British economy could also influence perceptions: Data on Wednesday showed average weekly pay in the three months to April was down 0.4 per cent, year-on-year, in inflation-adjusted terms - the biggest fall since the three months to September 2014.

Theresa May insisted the Government was "absolutely steadfast" in its commitment to the Northern Irish peace process as she faced questions on whether a DUP-Tory alliance would put fragile agreements at risk.

"They can't have it both ways, it has to be dealt with sensibly", she said.

"What we are doing in relation to the productive talks that we are holding with the Democratic Unionist Party is ensuring that it is possible to, with their support, give the stability to the UK Government that I think is necessary at this time".

While the DUP are deeply eurosceptic, they have balked at some of the practical implications of a so-called hard Brexit - including a potential loss of a "frictionless border" with the Republic of Ireland - and talks will touch on efforts to minimize the potential damage to Northern Ireland.